Work machines such as, for example, off-highway trucks and other heavy construction and mining machines, are used to perform many tasks. To effectively perform these tasks, the work machines require a power source that provides significant power to a transmission. The power source may be an engine such as, for example, a turbine engine, diesel engine, gasoline engine, or natural gas engine operated to generate a power output. The transmission must provide a range of gearing in order to allow the work machine to work at several different speeds while keeping the engine within a desired operating range. Typically, the work machines include a multi-speed transmission that generally includes a series of gears and is connected to the engine via a torque converter. The utilization of a torque converter helps to overcome problems of initial star-up and further provides a broader torque transmission range.
As described in U.S. Pat. No. 5,924,951 to Winzeler et al., a multi-speed transmission for a work machine typically includes a variety of gears and clutches that are disposed between an input member and an output member of a work machine. The input member is connected to, and is rotated by, an engine via a torque converter. The output member is used to move the work machine. The clutches are used to engage different combinations of gears that will connect the input member to the output member through a selected gear ratio. The selected gear ratio translates the rotational speed of the input member, as provided by the engine, to a desired rotational speed of the output member.
To generate the wide range of gear ratios required by the work machine, the multi-speed transmission typically includes a plurality of intermeshing gears and a corresponding plurality of clutches. Each of the gears may have different numbers of teeth to achieve the required gear ratios. In addition, differently designed clutches may be required to engage the different gears into the necessary gear ratios.
The manner in which the gears are engaged to provide the different gear ratios and the number of different gear ratios impacts the efficiency of the transmission and work machine. The larger the step and the more variable the step between gear ratios, the more an engine will deviate from the desired operating range. Energy and efficiency are lost when the work machine operates outside of the desired operating range.
The vehicle transmission of the present disclosure solves one or more of the problems set forth above.